1. Technical Field
This invention relates to devices for drying food and materials and, more particularly, to a food and materials dryer having a plurality of cylindrical hollow rotary tunnels each having an outer shell, an inner lining cylinder and an agitating auger, drying air being directed through the auger and between the outer shell and inner lining cylinder for drying material being agitated by the auger.
2. Description of the Prior Art
Various devices are known for drying hay, vegetables and other materials. Examples of such devices include Einarsson, U.S. Pat. No. 2,368,811, which discloses an apparatus for drying hay, vegetables, fish and the like comprising three compartments with spiral screws in each of them. Einarsson, however, discloses that air for drying is directed only into the central cylinder holding the spiral screw, which means that air cannot dry material at the far end of the spiral screw. Therefore, the majority of drying must be accomplished at the last segment of the spiral screw where air from the fan is blowing thereon, which may result in insufficient drying. Also, Einarsson does not disclose any agitating means other than a standard auger design, which may further restrict drying efficiency.
Another example found in the prior art is British Patent No. 926,877, issued to Rathery on May 22, 1963, which discloses an apparatus for drying grain comprising auger conveyors. Control means are provided for controlling the supply of hot air or gas to vary the heating of the material to be dried. However, once again, the material cannot be uniformly dried as air cannot reach some material in areas far from the air directing means.
Therefore, there is a need for a food and materials dryer which may efficiently dry a large amount of material placed therein.
Another problem encountered in using drying devices of the prior art is that the majority of such devices occupy a great deal of floor space in a plant, which results in wasted space and increased costs for the plant. Plants determine their cost by floor space, so it would be cost-efficient to stack devices to perform the same operations as can be performed by devices extending over a great deal of floor space. Presently, many of the drying processes used in plants involve very long conveyor belt screens which extend from 50 to 300 feet in length. Such drying processes are extremely cost-inefficient. There is therefore a need for a cost-efficient drying process which will occupy a minimum of floor space.
Therefore, an object of the present invention is to provide an improved food and materials dryer.
Another object of the present invention is to provide a food and materials dryer which may efficiently use floor space in a plant.
Yet another object of the present invention is to provide a food and materials dryer having an outer shell and an inner lining cylinder such that air may be directed between the outer and inner cylinders allowing food and materials at the far end of the cylinder to be dried in addition to materials at the near end of the cylinder.
Still another object of the present invention is to provide a food and materials dryer which may provide means for independently adjusting the rate of air flow, the temperature of the air and the rate of rotation of each auger.
Finally, an object of the present invention is to provide a food and materials dryer which is durable in construction and safe and efficient in use.